/*
 * Copyright 2011 Daniel Krieg
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.code.csf.locators;

import com.google.code.csf.ServiceLocator;

import java.util.List;

public class ServiceLocatorChain<ServiceType> implements ServiceLocator<ServiceType> {
    private final List<ServiceLocator<ServiceType>> serviceLocators;
    private ServiceLocator<ServiceType> cachedLocator;

    public ServiceLocatorChain(List<ServiceLocator<ServiceType>> serviceLocators) {
        this.serviceLocators = serviceLocators;
    }

    public ServiceType locate(Class<ServiceType> toLocate) {
        ServiceType located;
        if (cachedLocator == null) {
            located = chained(toLocate);
        } else {
            try {
                located = cachedLocator.locate(toLocate);
            } catch (Throwable throwable) {
                located = chained(toLocate);
            }
        }
        return located;
    }

    private ServiceType chained(Class<ServiceType> toLocate) {
        ServiceType located = null;
        for (ServiceLocator<ServiceType> serviceLocator : serviceLocators) {
            try {
                located = serviceLocator.locate(toLocate);
                if (located == null) {
                    continue;
                }
                cachedLocator = serviceLocator;
                break;
            } catch (Throwable throwable) {
                // ignore and continue
            }
        }
        return located;
    }

    public void release(ServiceType toRelease) {
        if (cachedLocator != null) {
            cachedLocator.release(toRelease);
        }
    }
}
